[Yoda]

"Extensor Action during (and as) the Loading Action will Flatten the Left
Wrist (6-B-1-D) -- which is normally Bent in the Swinger's Standard Adjusted
Address (10-9-A) -- as the Right Forearm Takeaway and Fanning execute the
Start Up. The Left Wrist will Swivel in conjunction with this Motion. -

-- Yoda"

The Backstroke Swivel occurs as the bridge between the Start Up (8-4) and the Backstroke (8-5). Until then, the Left Wrist (Bent / Byron Nelson or Flat / Jack Nicklaus) executes a Backstroke Hinge Action -- Vertical to the Horizontal Plane (Swinging / Horizontal Hinge Action) or the Inclined Plane (Hitting / Angled Hinge Action) -- as the Body Pivots (Zone One) and the Right Forearm 'traces' the Plane Line (Zone Three).

Just as the Finish Swivel (2-G and 12-5-3/3) serves as the bridge between the Follow Through (8-11) and Finish (8-12).

This topic cries out for a 'Video Answer'.

Duly noted.